Phencyclidine and the dynamics of mouse brain histamine

The effects of phencyclidine (PCP) on the dynamics of brain histamine (HA) were examined in the mouse brain. PCP (2-10 mg/kg i.p.) dose-dependently elevated the level of tele-methylhistamine (t-MH), a predominant metabolite of brain HA, without altering the HA level. PCP also enhanced the accumulation of t-MH after administration of pargyline hydrochloride (80 mg/kg i.p.). PCP at 5 mg/kg facilitated the HA depletion produced by (S)-α-fluoromethylhistidine markedly (50 mg/kg i.v.), a specific inhibitor of histidine decarboxylase. Metoprine (10 mg/kg i.p.), an inhibitor of HA-N-methyltransferase, decreased the t-MH level and increased the HA level. In the metoprine-treated mice, PCP at 10 mg/kg had no significant effect on the t-MH level, whereas it significantly increased the HA level. The increase in t-MH level after administration of PCP (5 mg/kg) was observed in various brain regions except the pons-medulla oblongata. These results suggest that, in mice, PCP increases the brain HA turnover possibly by facilitating the release of HA.